1. Field of the Invention
The present invention relates to a method for forming plate characters in a half-tone gravure platemaking process which provides the same character quality as is found in type printing.
1. Prior Art
FIGS. 2(a) through 2(c) show a process of printing a letter "A" formed by a plate character obtained by prior art half-tone gravure platemaking method. FIG. 2(a) shows a plate character "A" with a screen applied thereto, and the entire plate character consists of dot-form cells. The dot-form cells are formed by etching so that they have a shadow-portion dot percentage.
FIG. 2(b) shows a screen-applied plate character "A" of FIG. 2(a) upon which ink has been applied. When transfer-printing is performed onto paper, etc., the ink spreads and the blank-paper portions left by screen wires disappear, thus producing a letter "A" in which the entire character is black as shown in FIG. 2(c).
Thus, conventionally, plate characters are made up of dot form cells which have a shadow-portion dot percentage. Accordingly, the frames (or outlines) of the half-tone gravure characters (printed characters) are notched, and its quality is inferior to that of type-printed characters. Particularly, the quality of small characters is very low.
In an attempt to solve the problems described above, the inventor of the present application filed a patent application in Japan (Japanese Patent Application No. 1-171382). According to the method for forming plate characters in a half-tone gravure platemaking process described in this Japanese patent application, the ink in the character frame portions (or along the character outlines) is thick, and the character frame portions are far sharper than that obtained in type printing. Also, the character fill portions become solid black, accomplishing a high-quality character printing. However, this method has some problems. If aqueous inks which have a somewhat high fluidity are used, ink flow occurs in the character frame portions.